A flexible three-dimensional force tactile sensor and a preparation method thereof

Abstract

The application discloses a flexible three-dimensional force tactile sensor and a preparation method thereof, and belongs to the technical field of flexible tactile sensors.The application solves the problem that the wide linear range and high sensitivity of the existing flexible three-dimensional force tactile sensor are contradictory when perceiving the tangential force, and realizes the requirement that the sensitivity and the linear range can be flexibly adjusted and customized.The application constructs a sensitive layer with a transverse gradient change in modulus by means of sleeving and splicing materials with different moduli, so that the sensitivity of the sensitive layer changes transversely, the sensitive layer is used for adjusting and controlling the change of the sensitivity and the linear range of the sensor when detecting the tangential force, the non-uniform sensitivity of the transverse distribution of the sensitive layer is utilized to utilize the non-uniformity of the stress distribution on the surface of the sensitive layer under the tangential load, and then the performance of the device for perceiving the tangential force is improved, and the method is also effective under the normal load.The three-dimensional force sensor prepared by the method has high sensitivity and a wide linear range, and has wide application in three-dimensional force measurement and direction control.

Description

TECHNICAL FIELD

[0001] The present application relates to a flexible three-dimensional force tactile sensor constructed by a suit assembly splicing strategy and a preparation method thereof, and belongs to the technical field of flexible tactile sensors. BACKGROUND

[0002] Flexible tactile sensors have a wide range of applications in human-computer interaction, tactile perception, medical detection, and other fields due to their lightness, thinness, and flexibility. However, traditional flexible tactile sensors can only detect normal pressure, which cannot meet the needs of complex and diverse scenarios. Therefore, the development of flexible three-dimensional force tactile sensors that can simultaneously detect normal force and tangential force has become a research hotspot.

[0003] In recent years, researchers have proposed many different structures of flexible three-dimensional force sensors to improve their performance in sensing three-dimensional forces. For example, the invention patent with application number 202410438410.8 and the name "Flexible piezoresistive three-dimensional force sensor and its preparation method and application" constructs a three-dimensional force sensor by combining a prism protrusion with four piezoresistive sensing units made of pressure-sensitive material. The invention patent with application number 202010264842.3 and the name "A fully flexible capacitive three-dimensional force tactile sensor" constructs a three-dimensional force sensor by combining a square flexible sensing electrode and a circular flexible common electrode with a semi-circular groove structure, which has higher sensitivity and faster response speed. The invention patent with application number 202410950523.6 and the name "A three-dimensional force dual-mode flexible strain sensor for fabric detection" combines capacitive strain sensors and piezoelectric strain sensors to expand the application range of three-dimensional force sensors. The invention patent with application number 202510093447.6 and the name "Flexible multi-dimensional force sensor based on centripetal gradient magnetic field design and its preparation method" constructs a magnetic field with gradient magnetic flux, which makes the sensor have different response slopes at different stress stages and improves the force measurement range of the device. As a three-dimensional force sensor, its performance in detecting tangential force is very important. Few of the above sensor structure designs optimize the performance of the device in detecting tangential force. When sensing tangential force, the stress distribution on the surface of the sensor's sensitive layer is uneven. No researcher has proposed a corresponding structure design to take advantage of this feature, and the device still needs to solve the contradiction between wide linear range and high sensitivity under tangential force.

[0004] In summary, a novel structure is proposed to address the stress characteristics of three-dimensional force sensors under tangential force, thereby enhancing the performance of three-dimensional force sensors in sensing tangential force or multi-dimensional force, solving the contradiction between wide linear range and high sensitivity, and having a profound significance for the performance improvement and application expansion of three-dimensional force tactile sensors. SUMMARY

[0005] The present application provides a flexible three-dimensional force tactile sensor and a preparation method thereof to solve the problem that the wide linear range and high sensitivity of the existing flexible three-dimensional force tactile sensor are contradictory when perceiving tangential force.

[0006] The technical scheme of the present application is as follows:

[0007] One of the purposes of the present application is to provide a flexible three-dimensional force tactile sensor, which is sequentially provided with a convex, a sensitive layer and an interdigital electrode layer from top to bottom.

[0008] The sensitive layer is assembled and spliced by a plurality of materials with different moduli, and the low-modulus material is assembled and spliced in the high-modulus material; and the lower surface of the sensitive layer has a microstructure, and the upper surface is fixed by PI tape.

[0009] The convex and the PI tape on the upper surface of the sensitive layer are bonded by glue; and the interdigital electrode layer and the lower surface of the sensitive layer are assembled and packaged by PI tape.

[0010] Further limitation, the sensitive layer is assembled and spliced by N kinds of materials with different moduli, the high-modulus material of the square ring with an outer side length of 10 mm is the outermost layer, the square ring material with an outer side length of a N-1 , a N-2 , … a2 is the middle layer, and the square material with a side length of a1 is the innermost layer, wherein 0 < a1 < a2 < … < a N-2 < a N-1 < 10 mm, 1 < E 最外层 / E 最内层 ≤ 50.

[0011] Further limitation, N is an integer selected from 2-10.

[0012] Further limitation, the shape of the convex is a regular quadrangular pyramid, a circular truncated cone, a circular cylinder or a hemisphere; and the sensitive layer is assembled and spliced by square or circular low-modulus materials and square ring or circular ring high-modulus materials.

[0013] Further limitation, the microstructure is one or more of a regular pyramid array, a regular hemisphere array, a bionic structure, a gradient structure or a random microstructure, and the size of a single microstructure is 1-50 μm.

[0014] Further limitation, the interdigital electrode layer is composed of one common negative electrode and four separate positive electrodes.

[0015] Further limitation, the sensitive layer is a modulus-lateral-change material constructed by a pore-forming method, an ultraviolet curing method or a 3D multi-material printing method.

[0016] Further limitation, the sensitive layer is a sensitivity-lateral-change material constructed by constructing a microstructure with a size-lateral-change lower surface.

[0017] The second object of the present application is to provide a preparation method of the flexible three-dimensional force tactile sensor, which comprises the following steps:

[0018] (1) Preparation of the protrusion;

[0019] The polydimethylsiloxane prepolymer and the curing agent are mixed uniformly at a mass ratio of 10:1, poured into a mold, defoaming treatment is performed, and a PMMA sheet is covered on the mold, heated and cured, and after demolding, the protrusion is obtained;

[0020] (2) Preparation of the sensitive layer;

[0021] First, the polydimethylsiloxane prepolymer and the curing agent are mixed uniformly at a mass ratio of 10:1, poured into a mold with microstructure, heated and cured after defoaming treatment, and after demolding, a high-modulus flexible material with microstructure on one side is obtained, and conductive ink is sprayed on the side of the high-modulus flexible material with microstructure to obtain a low-sensitivity sensitive layer;

[0022] Then, the Ecoflex A liquid and the Ecoflex B liquid are mixed uniformly at a volume ratio of 1:1, poured into a mold with microstructure, cured at room temperature after defoaming treatment, and after demolding, a low-modulus flexible material with microstructure on one side is obtained, and conductive ink is sprayed on the side of the low-modulus flexible material with microstructure to obtain a high-sensitivity sensitive layer;

[0023] Finally, the low-sensitivity sensitive layer is cut into a square ring shape, the high-sensitivity sensitive layer is cut into a square shape, and the square size of the high-sensitivity sensitive layer is ensured to be consistent with the internal blank size of the low-sensitivity sensitive layer square ring, and the two are concentric and the corresponding edges are parallel; on the basis of ensuring that the microstructures of the two are located on the same side, the high-sensitivity sensitive layer is assembled and spliced in the internal blank of the low-sensitivity sensitive layer square ring, and the two are assembled into one by adhering the high-sensitivity sensitive layer to the other side opposite to the microstructure through the PI tape, to obtain a sensitive layer with microstructure on the lower surface and PI tape adhered on the upper surface;

[0024] (3) Preparation of the interdigital electrode layer;

[0025] The interdigital electrode layer is obtained by laser etching a rectangular PET electrode with silver on the surface;

[0026] (4) Preparation of the flexible three-dimensional force tactile sensor;

[0027] The lower surface of the protrusion prepared in (1) is adhered to the upper surface of the sensitive layer prepared in (2) by glue, and then the lower surface of the sensitive layer is assembled face to face with the interdigital electrode layer, and the PI tape is used for packaging, to obtain the flexible three-dimensional force tactile sensor.

[0028] Further limited, the heating curing temperature in (1) and (2) is 70 DEG C, and the time is 3 h.

[0029] Further limited, the conductive ink in (2) is mixed by CNTs, TPU and DMF, wherein the concentration of CNTs is 2 mg / ml, and the concentration of TPU is 0.67 mg / ml.

[0030] Further limited, before the high modulus flexible material and the low modulus flexible material in (2) are sprayed with the conductive ink, plasma surface treatment is carried out, and then spraying treatment is carried out at 80 DEG C.

[0031] Further limited, the plasma surface treatment gas is oxygen, and the time is 5 min.

[0032] The third object of the present application is to provide another flexible three-dimensional force tactile sensor, and the specific sensitive layer is a modulus transverse change material constructed by a pore-forming method, an ultraviolet curing method or a 3D multi-material printing method, or a material with transversely changed sensitivity by constructing a microstructure with transversely changed size on the lower surface of the sensitive layer.

[0033] The fourth object of the present application is to provide an application of the above-mentioned flexible three-dimensional force tactile sensor, and the specific application is used for measuring three-dimensional force of interface, sliding detection or game control scene.

[0034] The present application has the following advantages:

[0035] The present application constructs a sensitive layer with transversely gradient change of modulus by means of assembling and splicing different modulus materials, so that the sensitivity transversely changes, and the sensitive layer is used for adjusting the change of sensitivity and linear range of the sensor when detecting tangential force, the non-uniformity of stress distribution on the surface of the sensitive layer under the action of tangential load is utilized by using the non-uniform sensitivity of the sensitive layer transversely distributed, and then the performance of the device when perceiving three-dimensional force is improved, the contradiction between high sensitivity and wide linear range of the sensor when perceiving tangential force is effectively reconciled, and the performance of the three-dimensional force sensor is improved.

[0036] (1) the sensitivity of the three-dimensional force sensor when perceiving tangential force can be improved, the contradiction between high sensitivity and wide linear range is reconciled, and the effect is better than simply adjusting the modulus of the whole sensitive layer;

[0037] (2) the strategy can also reconcile the contradiction between high sensitivity and wide linear range when detecting normal force;

[0038] (3) the strategy can realize flexible and rich adjustment of the performance of the three-dimensional force sensor in multiple ways, the sensitivity and linear range of the sensor can be flexibly adjusted by adjusting the number of splicing, the size of splicing and the modulus difference, and the performance of the three-dimensional force sensor for detecting normal force and tangential force can be customized.

[0039] (4) The three-dimensional force sensor prepared by the application has high sensitivity and wide linear range, can measure the three-dimensional force of the interface, and is applied to scenes such as mechanical arm gripping and slip detection;

[0040] (5) The three-dimensional force sensor prepared by the application has small angle resolution, and can be applied to angle and direction related control, such as game control. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 The structure diagram of the flexible three-dimensional force tactile sensor provided for embodiment 1 of the application;

[0042] Figure 2 The preparation flowchart of the flexible three-dimensional force tactile sensor provided for embodiment 1 of the application;

[0043] Figure 3 The SEM photos of the sensitive layer set splicing part prepared for embodiment 1 (different magnifications);

[0044] Figure 4 The schematic diagram of the interdigital electrode layer prepared for embodiment 1;

[0045] Figure 5 The schematic diagram when N different modulus sensitive layers are spliced (2≤N≤10) (unit: mm), wherein (a) N=2, (b) N>2;

[0046] Figure 6 The E1 element area division schematic diagram when N different modulus sensitive layers are spliced (unit: mm);

[0047] Figure 7 The performance comparison diagram of the flexible three-dimensional force tactile sensors prepared for embodiment 1 and comparative examples 1-3, wherein (a) is the force-electricity curve under the tangential force Fx, (b) is the force-electricity curve under the normal force Fz, and (c) is the linear sensing factor (the product of sensitivity and linear range);

[0048] Figure 8 The performance comparison diagram of the flexible three-dimensional force tactile sensors prepared for embodiments 1-3, wherein (a) is the force-electricity curve under the tangential force Fx, (b) is the force-electricity curve under the normal force Fz, and (c) is the linear sensing factor (the product of sensitivity and linear range);

[0049] Figure 9The results of finite element simulations of the flexible three-dimensional force sensors prepared in Examples 1-3 and Comparative Examples 1-2 under a tangential force Fx of 1 N are shown in the figure. (a) is a cloud map of stress and displacement distribution on the surface of the sensitive layer. Specifically, (i) is the stress distribution, (ii) is the displacement distribution, (b) is the stress distribution curve on the surface of the sensitive layer along the x-axis, (c) is the displacement distribution curve on the surface of the sensitive layer along the x-axis, and (d) is a sensitivity comparison diagram under tangential force.

[0050] Figure 10 The results of finite element simulations of the flexible three-dimensional force sensors prepared in Examples 1-3 and Comparative Examples 1-2 under a normal force Fz of 1 N are shown in the figure. (a) is a cloud map of stress and displacement distribution on the surface of the sensitive layer, specifically (i) stress distribution, (ii) displacement distribution, (b) stress distribution curve on the surface of the sensitive layer along the x-axis, (c) displacement distribution curve on the surface of the sensitive layer along the x-axis, and (d) sensitivity comparison diagram under normal force.

[0051] Figure 11 The results of finite element simulation are shown for two types of modulus sensitive layer sets spliced ​​together, when the tangential force Fx is 1 N and the modulus ratio of the outer and inner layers changes. Among them, (a) is the stress and displacement distribution cloud map of the sensitive layer surface, specifically (i) is the stress distribution, (ii) is the displacement distribution, (b) is the stress distribution curve of the sensitive layer surface along the x-axis, (c) is the displacement distribution curve of the sensitive layer surface along the x-axis, and (d) is the relative magnitude of the equivalent sensitivity.

[0052] Figure 12 The results of finite element simulation are shown for two types of sensitive layer sets spliced ​​together, with a normal force Fz of 1 N and a change in the modulus ratio of the outer and inner layers. Among them, (a) is the stress and displacement distribution cloud map of the sensitive layer surface, specifically (i) is the stress distribution, (ii) is the displacement distribution, (b) is the stress distribution curve of the sensitive layer surface along the x-axis, (c) is the displacement distribution curve of the sensitive layer surface along the x-axis, and (d) is the relative magnitude of the equivalent sensitivity.

[0053] Figure 13 The results of finite element simulation under a tangential force Fx=1 N are shown for the splicing of three different sizes of sensitive layers with different moduli. Among them, (a) the surface stress and displacement distribution cloud map of the sensitive layer, specifically (i) stress distribution, (ii) displacement distribution, (b) the surface stress distribution curve of the sensitive layer along the x-axis, (c) the surface displacement distribution curve of the sensitive layer along the x-axis, and (d) the relative magnitude of the equivalent sensitivity.

[0054] Figure 14The results of finite element simulation under normal force Fz=1 N are shown for the splicing of three different sizes of sensitive layers with different moduli. Among them, (a) the surface stress and displacement distribution cloud map of the sensitive layer, (i) stress distribution, (ii) displacement distribution, (b) surface stress distribution curve of the sensitive layer along the x-axis, (c) surface displacement distribution curve of the sensitive layer along the x-axis, and (d) the relative magnitude of equivalent sensitivity.

[0055] Figure 15 The results of finite element simulation are shown for a three-modulus sensitive layer assembly, with a tangential force Fx of 1 N and a change in the modulus ratio of the outer and inner layers. Among them, (a) is the stress and displacement distribution cloud map of the sensitive layer surface, specifically (i) is the stress distribution, (ii) is the displacement distribution, (b) is the stress distribution curve of the sensitive layer surface along the x-axis, (c) is the displacement distribution curve of the sensitive layer surface along the x-axis, and (d) is the relative magnitude of the equivalent sensitivity.

[0056] Figure 16 The results of finite element simulation are shown for the splicing of three types of modulus sensitive layers, when the normal force Fz is 1 N and the modulus ratio of the outer and inner layers changes. Among them, (a) is the stress and displacement distribution cloud map of the sensitive layer surface, specifically (i) is the stress distribution, (ii) is the displacement distribution, (b) is the stress distribution curve of the sensitive layer surface along the x-axis, (c) is the displacement distribution curve of the sensitive layer surface along the x-axis, and (d) is the relative magnitude of the equivalent sensitivity.

[0057] Figure 17 Finite element simulation results for sensitive layer sets with different splicing numbers under tangential force Fx=1 N, including (a) surface stress and displacement distribution cloud map of sensitive layer, specifically (i) stress distribution, (ii) displacement distribution, (b) surface stress distribution curve of sensitive layer along the x-axis, (c) surface displacement distribution curve of sensitive layer along the x-axis, and (d) relative magnitude of equivalent sensitivity;

[0058] Figure 18 Finite element simulation results for sensitive layer sets with different numbers of splices under normal force Fz=1 N, including (a) surface stress and displacement distribution cloud map of sensitive layer, specifically (i) stress distribution, (ii) displacement distribution, (b) surface stress distribution curve of sensitive layer along the x-axis, (c) surface displacement distribution curve of sensitive layer along the x-axis, and (d) relative magnitude of equivalent sensitivity;

[0059] Figure 19 Other performance characteristics of the flexible three-dimensional force tactile sensor prepared in Example 1 under tangential load, where (a) is stepped loading, (b) is loading at different frequencies, (c) is the detection limit, (d) is the response and recovery time, and (e) is the cyclic fatigue test;

[0060] Figure 20Other performance characteristics of the flexible three-dimensional force tactile sensor prepared in Example 1 under normal load, where (a) is stepped loading, (b) is loading at different frequencies, (c) is the detection limit, (d) is the response and recovery time, and (e) is the cyclic fatigue test;

[0061] Figure 21 Schematic diagram of other types of LVS sensitive layers;

[0062] Figure 22 The three-dimensional force tactile sensor prepared for Example 1 is applied to the measurement of three-dimensional force on the gripping interface of a robotic arm, where (a) is the key action of the robotic arm gripping a glass, and (b) is the real-time test result curve of the three-dimensional force on the gripping interface.

[0063] Figure 23 The three-dimensional force tactile sensor prepared in Example 1 is applied to slip detection, where (a) is the scene where slip occurs, (b) is the real-time three-dimensional force curve of the interface during the test process, (c) is the DWT processing of the Fz force signal, (d) is the DWT processing of the Fx force signal, and (e) is the DWT processing of the Fy force signal.

[0064] Figure 24 The test results of the sensor prepared in Example 1 for tangential force at different angles are shown in (a) for Δα=30°, (b) for Δα=15°, and (c) for Δα=10°.

[0065] Figure 25 The three-dimensional force tactile sensor prepared for Example 1 is applied to game control, where (a) is the "Snake" game control system, and (b) is the effect of game control;

[0066] In the diagram, 1-protrusion, 2-PI tape, 3-sensitive layer, 4-conductive layer, 5-interdigital electrode, and 6-flexible PET substrate. Detailed Implementation

[0067] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0068] Example 1

[0069] like Figure 1 and Figure 2 As shown, the method for fabricating a flexible three-dimensional force-tactile sensor in this embodiment includes the following steps:

[0070] (1) Preparation of protrusions;

[0071] The polydimethylsiloxane prepolymer of Dow Corning DC184 and the curing agent were mixed evenly at a mass ratio of 10:1. The mixture was poured into a polytetrafluoroethylene mold, ensuring the liquid volume slightly exceeded the mold's capacity. The mold was then placed under a vacuum pump for degassing. A smooth PMMA sheet was then placed over the mold opening to remove excess liquid. A 50 g weight was added to the PMMA sheet, and the mold was placed in an oven at 70°C for 3 hours for curing. After demolding, a truncated square pyramid-shaped protrusion 1 was obtained and set aside. The specific dimensions of protrusion 1 are: upper surface 9.5 × 9.5 mm, lower surface 10 × 10 mm, and height 4.2 mm.

[0072] (2) Preparation of the sensitive layer;

[0073] ① Mix Dow Corning DC184 polydimethylsiloxane prepolymer and curing agent evenly at a mass ratio of 10:1, pour into a mold with microstructure (microstructure is random microstructure, with each individual microstructure having a diameter of about 50 μm), vacuum, level and de-bubbling treatment, place in an oven and keep warm at 70℃ for 3 h for curing treatment, demold, and obtain a high modulus flexible material with a thickness of about 500 μm on one side with microstructure. The microstructure side of the high-modulus flexible material was subjected to plasma surface treatment (oxygen gas, time 5 min), placed on an 80℃ hot stage, and sprayed (using an ultrasonic spraying device, spraying gas pressure 0.4 MPa, ultrasonic power 3.5 W, conductive ink flow rate 0.225 ml / min, the thickness of the conductive layer obtained after spraying is 1-2 μm) with conductive ink (conductive ink is a mixture of CNTs, TPU and DMF, where the concentration of CNTs is 2 mg / ml and the concentration of TPU is 0.67 mg / ml), to obtain a low-sensitivity sensitive layer with conductive layer 4.

[0074] ② Mix Ecoflex A liquid and Ecoflex B liquid of Smooth-On Ecoflex 00-30 at a volume ratio of 1:1, pour into the same microstructure mold used in ①, evacuate using a vacuum pump, place the mold on a flow platform, cure at room temperature for 4 hours, demold, and obtain a low-modulus flexible material with a thickness of about 500 μm and a microstructure on one side. Perform plasma surface treatment on the microstructure side of the low-modulus flexible material (oxygen gas, time 5 min), place on an 80℃ hot stage, and spray (using an ultrasonic spraying device, spraying pressure 0.4 MPa, ultrasonic power 3.5 W, conductive ink flow rate 0.225 ml / min, the conductive layer thickness obtained after spraying is 1-2 μm) with conductive ink (conductive ink is a mixture of CNTs, TPU and DMF, where the concentration of CNTs is 2 mg / ml and the concentration of TPU is 0.67 mg / ml), to obtain a highly sensitive layer with conductive layer 4.

[0075] ③ Use a large square cutter (15×15 mm) to cut the low-sensitivity layer prepared in ① (the effective area is only 10x10 mm, the extra part is for easy encapsulation), to obtain a large square low-sensitivity layer. Then use a small square cutter (6×6 mm) to continue cutting the center area of ​​the large square low-sensitivity layer, to obtain a square annular low-sensitivity layer. Use a small square cutter (6×6 mm) to cut the high-sensitivity layer, to obtain a small square high-sensitivity layer. On the basis of ensuring that the microstructures of the small square high-sensitivity layer and the square annular low-sensitivity layer are on the same side, the small square high-sensitivity layer is assembled into a single unit in the inner square blank of the square annular low-sensitivity layer, and the two are assembled into a single unit by adhering PI tape 2 to the opposite side of the microstructure, to obtain a sensitive layer 3 with a microstructure on the lower surface and PI tape 2 adhered to the upper surface.

[0076] The microstructure of the splicing area of ​​the obtained sensitive layer 3 was characterized, and the SEM images are as follows: Figure 3 As stated, by Figure 3 It can be seen that the gaps at the joints of the kit are very small, and the high and low sensitivity sensitive layers of the kit have the same random microstructure. The size of a single microstructure is about 50 μm, and a carbon nanotube conductive layer is attached to the surface of the microstructure.

[0077] (3) Fabrication of the interdigitated electrode layer;

[0078] An interdigitated electrode layer with interdigitated electrodes 5 is obtained by laser etching of a rectangular flexible PET substrate 6 with metallic silver on its surface; for example... Figure 4As shown, the interdigital electrode 5 consists of a common negative electrode and four individual positive electrodes, with a total working area of ​​10×10 mm; each unit is 5×5 mm, each unit contains 10 fingers, and the finger gaps are 150 μm.

[0079] (4) Fabrication of a flexible three-dimensional force-tactile sensor;

[0080] The lower surface of the protrusion 1 prepared in (1) is bonded to the PI tape 2 on the upper surface of the sensitive layer 3 prepared in (2) with 8008 glue. Then, the lower surface of the sensitive layer 3 is aligned with the interdigital electrode 5 of the interdigital electrode layer and assembled. The sensor is encapsulated with PI tape to obtain a flexible three-dimensional force tactile sensor, abbreviated as LVS-a6 (representing a sensor prepared with a laterally varying sensitivity sensitive layer).

[0081] Example 2

[0082] The difference between this embodiment and embodiment 1 is that: (2) In the preparation of the sensitive layer, a small square cutter (4×4 mm) is used to prepare the sensitive layer. The remaining process steps and parameters are the same as in embodiment 1, and a flexible three-dimensional force tactile sensor, abbreviated as LVS-a4, is obtained.

[0083] Example 3

[0084] The difference between this embodiment and embodiment 1 is that: (2) In the preparation of the sensitive layer, a small square cutter (8×8 mm) is used to prepare the sensitive layer. The remaining process steps and parameters are the same as in embodiment 1, and a flexible three-dimensional force tactile sensor, abbreviated as LVS-a8, is obtained.

[0085] Comparative Example 1

[0086] The difference between this comparative example and Example 1 is that: (2) the preparation of the sensitive layer, specifically, the low-sensitivity sensitive layer prepared by cutting with a large square cutter (15×15 mm) is directly used as the sensor sensitive layer. The remaining process steps and parameters are the same as in Example 1, and a flexible three-dimensional force tactile sensor is obtained, which is abbreviated as LS (representing a low-sensitivity sensitive layer sensor prepared with a pure high-modulus sensitive layer).

[0087] Comparative Example 2

[0088] The difference between this comparative example and Example 1 is: (2) Preparation of the sensitive layer. Specifically, the high-sensitivity sensitive layer prepared by cutting with a large square cutter (15×15 mm) is directly used as the sensor sensitive layer. The remaining process steps and parameters are the same as in Example 1, and a flexible three-dimensional force tactile sensor is obtained, which is abbreviated as HS (representing a high-sensitivity sensitive layer sensor prepared with a pure low-modulus sensitive layer).

[0089] Comparative Example 3

[0090] The difference between this comparative example and Example 1 is as follows: (2) Preparation of the sensitive layer: Specifically, Dow Corning DC184 polydimethylsiloxane prepolymer and curing agent are mixed evenly in a mass ratio of 10:1 to obtain PDMS adhesive to be cured, and set aside; Smooth-On Ecoflex 00-30 Ecoflex A liquid and Ecoflex B liquid are mixed evenly in a volume ratio of 1:1 to obtain Ecoflex adhesive to be cured, and set aside; after mixing the PDMS adhesive to be cured and the Ecoflex adhesive to be cured in a volume ratio of 1:2, it is poured into a mold with microstructure, and after vacuuming, leveling and debubbling treatment, it is placed in an oven and kept warm at 70°C for 3 hours for curing treatment, and then demolded to obtain a medium modulus flexible material with microstructure on one side. The microstructured side of the medium-modulus flexible material was subjected to plasma surface treatment (oxygen gas, time 5 min), placed on an 80°C hot stage, and coated with conductive ink (using an ultrasonic spraying device, spraying pressure 0.4 MPa, ultrasonic power 3.5 W, conductive ink flow rate 0.225 ml / min, resulting in a conductive layer thickness of 1-2 μm) to obtain a medium-sensitivity layer. The medium-sensitivity layer prepared above was cut with a large-size square cutter (15×15 mm) and used directly as the sensor's sensitive layer. The remaining process steps and parameters were the same as in Example 1, resulting in a flexible three-dimensional force tactile sensor, abbreviated as MS (representing a medium-sensitivity layer sensor prepared with pure medium-modulus sensitive layer).

[0091] Application examples

[0092] A single three-dimensional force sensor comprises four elements, E1-E4. All four elements are fabricated identically, and theoretically, their output electrical signals are similar under the same load. However, actual assembly and packaging processes can cause inconsistencies in the output electrical signals of the four elements. Normalization can be used to normalize the electrical signal of each element to near the average value of the four elements, thus reducing these inconsistencies. The normalized data for the four elements are similar, and each element can independently characterize the device's performance. Here, the normalized data of element E1 is selected as representative for different devices (the equivalent sensitivity in simulation also extracts data from the E1 region). Furthermore, due to the symmetry of the four element arrangement, the device's performance when sensing Fx and Fy is approximately the same. Here, the data under Fx is used as the representative data for sensing tangential force, and the data under Fz is used as the representative data for sensing normal force.

[0093] (1) The performance of the flexible three-dimensional force tactile sensors prepared in Example 1 and Comparative Examples 1-3 was characterized, and the results are as follows: Figure 7As shown, it can be seen from the figure that compared with LS, MS, and HS sensors, the LVS sensor not only improves the sensor sensitivity but also has a good linear range. From Figure 7 as shown in (a), under the tangential force Fx, the LVS device has a sensitivity of 14.59 μA / N and a linear range of 0 - 10 N. From Figure 7 as shown in (b), under the normal force Fz, the LVS device has a sensitivity of 17.57 μA / N and a linear range of 0 - 10 N. To evaluate the comprehensive performance of the device and whether it兼顾 high sensitivity and wide linear range, the comprehensive performance of the sensor can be intuitively presented by calculating the size of the product LSF (linear sensing factor) of sensitivity and linear range. The larger this value, the better the comprehensive performance of the sensor. The sensitivity and linear range product LSF of different sensors are as Figure 7 shown in (c). It can be seen from the figure that whether under tangential force or normal force, the LSF of the LVS sensor is the largest, indicating that whether tangentially or normally, the LVS sensor兼顾 high sensitivity and wide linear range, and the effect is better under tangential force.

[0094] (2)Characterize the performance of the flexible three-dimensional force tactile sensors prepared in the above Examples 1 - 3. The results are as Figure 8 shown. It can be seen from the figure that under the two modulus-sensitive layer splicing modes, as the inner layer size a gradually increases (the splicing size is shown in Figure 5 (a)), the sensitivity of the sensor gradually increases, but the linear range gradually decreases. By comparing the LSF of different sensors, when a is 6 (Example 1), the sensor performance is the best.

[0095] (3)To discuss the influence of the change in splicing size on the device performance when the sensitive layer is composed of two materials with different moduli and is spliced in a sleeve manner, it is discussed through finite element simulation as follows:

[0096] As Figure 5 shown in (a), the side length of the inner layer material is a, and the outer side length of the outer layer material is 10, where​​​​​​​​​​(The simulation results are under the normal force Fz = 1 N.)As can be seen from the figure, with the change of the size of the inner Ecoflex, the sensitivity also changes. The larger the value of a, the greater the sensitivity, and it is between the LS and HS sensitivities. From Figure 9 (d) and Figure 10 it can be seen from (d) that the simulation and experimental laws are consistent. It can be seen that by adjusting the splicing size, the effective adjustment and customization of the device performance can be achieved.

[0098] (4)To discuss the influence of the difference between the outer layer material modulus and the inner layer material modulus on the device performance when the sensitive layer is composed of two materials with different moduli spliced in a sleeve, it is discussed through finite element simulation as follows:

[0099] As Figure 5 shown in (a), fix the size of the inner layer a = 6 unchanged, keep the modulus of the inner layer material E 内 = 0.1 MPa unchanged, and adjust the change of the modulus of the outer layer material E 外 . Let E 外 / E 内 = R, where 1 < R ≤ 50, and the results under 5 kinds of modulus differences are simulated, that is, the cases when R = 2, 5, 10, 30, 50.

[0100] The simulation results are as Figure 11 and 12 shown ( Figure 11 is the simulation result under the tangential force Fx = 1 N, Figure 12 is the simulation result under the normal force Fz = 1 N). As can be seen from the figure, with the continuous increase of the outer layer modulus, the stress and displacement distribution gaps between the outer layer and the inner layer regions become larger and larger, and the device sensitivity continuously decreases. It can be seen that by adjusting the modulus difference between the inner and outer layers, the effective adjustment and customization of the device performance can be achieved.

[0101] (5)To discuss the influence of the change of the splicing size on the sensor performance when the sensitive layer is composed of three materials with different moduli spliced in a sleeve, it is discussed through finite element simulation as follows:

[0102] As Figure 5 shown in (b), fix the moduli of the three sensitive layers, where the moduli of the inner layer, middle layer and outer layer are 0.1, 0.5 and 1 MPa respectively, and adjust the side length a1 of the inner layer material and the outer side length a2 of the middle layer material, where 0 < a1 < a2 < 10, and the results under 6 kinds of sleeve splicing sizes are simulated, that is, the cases when (a1, a2) = (2, 4), (2, 6), (2, 8), (4, 6), (4, 8), (6, 8).

[0103] The simulation results are as Figure 13 and 14 shown ( Figure 13It is the simulation result under the tangential force Fx = 1 N. Figure 14 It is the simulation result under the normal force Fz = 1 N). As can be seen from the figure, with the change of the sizes of the inner layer and the middle layer, the stress and displacement distributions in the inner layer, middle layer and outer layer regions also change accordingly. The sensitivity of the device is jointly affected by a1 and a2, showing a spatial distribution pattern. It can be seen that by adjusting the sizes of the inner layer and the middle layer, more flexible and richer adjustment and customization of the device performance can be achieved.

[0104] (6) In order to discuss the influence of the change of modulus difference on the device performance when the sensitive layer is composed of three materials with different moduli and is assembled by splicing, it is discussed through finite element simulation as follows:

[0105] As Figure 5 shown in (b), fix the sizes of the inner layer and the middle layer, where the side length of the inner layer a1 = 3.33 and the outer side length of the middle layer a2 = 6.67. Keep the modulus of the inner layer material E 内 = 0.1 MPa unchanged, and adjust the change of the modulus of the outer layer material E 外 and the modulus of the middle layer material E 中 . Let E 外 / E 内 = R1, E 中 / E 内 = R2, where 1 < R2 < R1 ≤ 50. The results under 6 kinds of modulus differences are simulated, that is, the cases when (R1, R2) = (5, 2.5), (10, 2.5), (10, 5), (20, 2.5), (20, 5), (20, 10).

[0106] The simulation results are as Figure 15 and Figure 16 shown ( Figure 15 is the simulation result under the tangential force Fx = 1 N, Figure 16 is the simulation result under the normal force Fz = 1 N). As can be seen from the figure, with the change of the moduli of the middle layer and the outer layer, the stress and displacement distributions in the inner layer, middle layer and outer layer regions also change accordingly. The device performance is jointly affected by R1 and R2, showing a spatial distribution pattern. It can be seen that by adjusting the modulus difference between the three sensitive layer materials, more flexible and richer adjustment and customization of the device performance can be achieved.

[0107] (7) In order to discuss the influence of the change of the number of types of sensitive layers participating in splicing on the performance of the spliced device when using the splicing strategy, it is discussed through finite element simulation as follows:

[0108] As Figure 5 shown, when adjusting the number of splicing types, the splicing size is evenly divided horizontally; the material modulus increases uniformly in a stepped manner from the innermost layer to the outermost layer. Fix E 最内 = 0.1 MPa, E 最外=1 MPa, assuming the sensitive layer is spliced ​​from N sets of materials with different moduli, where 2≤N≤10, the results under 5 different splicing numbers were simulated, namely N=2, 3, 5, 7, and 10.

[0109] Simulation results are as follows Figure 17 and Figure 18 As shown ( Figure 17 These are simulation results under a tangential force Fx = 1 N. Figure 18 (These are simulation results under a normal force Fz=1 N). As shown in the figure, with the increase of the number of splice inlets, the stress and displacement distribution in the sensitive layer with different modulus materials also change. The device performance is greatly affected by the number of splice inlets. The tangential sensitivity first decreases and then increases with the increase of N, indicating that the more splice inlets there are, the more thoroughly the unevenly distributed stress is utilized. The normal sensitivity decreases continuously with the increase of N. When N≥5, the change in sensitivity is not obvious. The more splices there are, the more complex the mutual constraint between layers becomes, and the more difficult the actual splicing operation becomes. From a practical point of view, it is better to choose N=2 or 3.

[0110] Furthermore, the approximate expression for the force-electric curve of the assembled device is derived, as follows:

[0111] In the modular assembly mode, by combining the normal force-electric curve data of the unassembled components in the experiment with the average normal force data of each region obtained from the simulation, a rough prediction of the force-electric curve trend of the assembled components can be achieved. The principle is as follows:

[0112] When the number of sensitive layers involved in the splicing is N, the splicing situation is as follows: Figure 5 As shown, since the size distribution of the four components is similar, we will take component E1 as the object of analysis here. Figure 6 This diagram illustrates the area division of the E1 component after splicing. The different splicing areas are divided into A1-A1. N Electrical signals are exemplified by current.

[0113] Because A1-A N The regions are connected in parallel in the circuit, so the total current in region E1 is the sum of the currents provided by each region, as shown in equation (1).

[0114] (1)

[0115] in, I E1 This represents the total current in region E1. A represents i The current supplied to the region.

[0116] A i The current supplied by the region can be expressed as in the unspliced ​​state (i.e., all materials in region E1 are A). iCurrent magnitude of the area material After splicing A i Percentage of area occupied by the region The product of , as shown in equation (2);

[0117] (2)

[0118] in and The expressions are (3) and (4) respectively;

[0119] (3)

[0120] (4)

[0121] in Indicates that after splicing, A i The average normal force on the region under load F (which can be obtained by extracting simulation data). A represents i The functional relationship between normal force and current in the unjoined region (which can be obtained experimentally); Indicates that after splicing, A i The area of ​​the region This represents the total area of ​​region E1.

[0122] set up , and Let A represent the external loads Fz, Fx, and Fy, respectively. i The average normal force on the region can be obtained by combining equations (1)-(4) to obtain the approximate expression (5)-(7) for the current in region E1 under the corresponding uniaxial force.

[0123] (5)

[0124] (6)

[0125] (7)

[0126] in, , and λz, λx, and λy represent the total output current in the E1 region under uniaxial forces Fz, Fx, and Fy, respectively. λz, λx, and λy represent the correction coefficients of the device in the z, x, and y directions, respectively, which can be obtained by comparing experimental data. This formula can be used to predict the electromechanical curve of the spliced ​​device, and further predict a more comprehensive performance of the spliced ​​device, which is convenient for guiding the optimization of process parameters and the customization of device performance.

[0127] Figure 19Other performance characteristics of the sensor prepared in Example 1 under tangential load Fx are shown. As can be seen from the figure, the device exhibits good step response under Fx=0-10 N step loading; the device can sense tangential loads of different frequencies; the lowest detection limit is 10 mN; the response and recovery times are 100 ms and 90 ms, respectively; and it shows good stability after 7200 cycles of testing under load of Fx=0.1-1 N.

[0128] Figure 20 Other performance characteristics of the sensor prepared in Example 1 under normal load Fz are shown. As can be seen from the figure, the device exhibits good step response under Fz=0-10 N step loading; the device can sense normal loads of different frequencies; the lowest detection limit is 30 mN; the response and recovery times are 70 ms and 50 ms, respectively; and it shows good stability after 7200 cycles of testing under load of Fz=0.1-1 N.

[0129] (8) The sensitive layer with lateral sensitivity variation provided by the present invention can also be a material with lateral modulus variation constructed by means of pore-forming method, ultraviolet curing method or 3D multi-material printing method, thereby constructing a sensitive layer with lateral sensitivity variation; and by changing the microstructure size of the lower surface of the sensitive layer, a microstructure with lateral size variation is constructed, thereby constructing a sensitive layer with lateral sensitivity variation, such as Figure 21 As shown.

[0130] (9) The flexible three-dimensional force sensor prepared in Example 1 was applied to a robotic arm, such as... Figure 22 As shown, the real-time measurement results of the three-dimensional force at the gripping interface during the process of the robotic arm grasping the glass are as follows: Figure 22 As shown in (b), the prepared three-dimensional force sensor can measure the three-axis force components of the gripping interface in real time and accurately reflect the changes in the component forces under key actions during gripping. For example, 1. When clamping, the interface Fz and Fx increase (indicating that the mechanical claw is difficult to clamp in parallel and there is a tangential force component), 2. When lifting the cup or 3. When pouring water into the cup, Fx and Fy decrease (the tangential force of the interface increases due to gravity), 4. When putting down and releasing, the three-axis force fluctuates and decreases to 0. It can be seen that the prepared sensor can realize real-time and accurate measurement of three-dimensional force.

[0131] (10) The flexible three-dimensional force tactile sensor prepared in Example 1 was applied to the detection of slippage phenomena during three-dimensional force detection at the interface, such as... Figure 23 As shown, Figure 23 (a) Sliding is a high-frequency action. The scenario of sliding is simulated by rapidly moving the upper pressure plate left and right using the testing device, such as... Figure 23 (b) The entire testing process is divided into 5 phases: I. Slow loading phase, II. Holding phase, III. Sliding phase, IV. Holding phase, and V. Slow unloading phase; as follows Figure 23(c)-(e) By performing Discrete Wavelet Transform (DWT) on the triaxial force signal output by the sensor, the high-frequency components in the signal can be extracted, thereby discovering the occurrence and timing of the slippage. By combining the data after transformation in the three directions and reasonably setting the detail coefficient threshold, the occurrence of slippage and its approximate direction can be accurately determined.

[0132] (11) The flexible three-dimensional force tactile sensor prepared in Example 1 was used to test tangential forces at different angles, and the results are as follows: Figure 24 As shown, during the test, the normal force Fz = 4 N and the tangential force Ft = 1.6 N remained constant. The angle α between the tangential force and the positive X-axis changed with different advances Δα within the range of 0-360°. Figure 24 As shown in (a)-(c), the prepared three-dimensional force sensor can accurately distinguish tangential forces at different angles, with the smallest distinguishable angle change being 10°.

[0133] (12) The flexible three-dimensional force tactile sensor prepared in Example 1 can be used to control the game, and the results are as follows: Figure 25 As shown, Figure 25 (a) A "Snake" game control system was constructed by combining the prepared sensors with back-end signal processing and related software modules; Figure 25 (b) It can be seen that the prepared three-dimensional force sensor can be used as a game controller to control the game character. By applying forces of different magnitudes and directions to the sensor, the movement of the target can be controlled. The magnitude of the normal force can be used as a criterion for starting or pausing the game. The game can be started when the normal force is ≥1 N, otherwise the game is paused. The tangential force can be used as a direction vector to control the movement direction of the game character.

[0134] The above description is only a preferred embodiment of the present invention. Given that those skilled in the art can make appropriate changes and modifications to the above embodiments, the present invention is not limited to the specific embodiments described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention.

Claims

1. A flexible three-dimensional force tactile sensor, characterized in that, From top to bottom, the layers are: protrusions, sensitive layer, and interdigitated electrode layer. The sensitive layer is composed of multiple materials with different moduli spliced ​​together, with low-modulus materials spliced ​​within high-modulus materials; and the lower surface of the sensitive layer has a microstructure, while the upper surface is fixed by PI tape. The protrusions are bonded to the upper surface of the sensitive layer with PI tape using adhesive; the interdigitated electrode layer is assembled with the lower surface of the sensitive layer and then encapsulated with PI tape. The sensitive layer is composed of N sets of materials with different moduli, with a high-modulus square ring material with an outer side length of 10 mm as the outermost layer, and the outer side lengths are successively a. N-1 a N-2 ...a2 is a square ring material as the middle layer, and a1 is a square material as the inner layer, where 0... <a1<a2<…<a N-2 N-1 <10 mm, 1 <E 最外层 / E 最内层 ≤50.​ 2. The flexible three-dimensional force tactile sensor according to claim 1, characterized in that, The N is selected from an integer between 2 and 10.

3. The flexible three-dimensional force tactile sensor according to claim 1, characterized in that, The protrusions are shaped like a regular square frustum, a frustum of a cone, a cylinder, or a hemisphere; the sensitive layer is composed of square or circular low-modulus materials and square or circular high-modulus materials; the microstructure is one or more of the following: regular pyramid array, regular hemispherical array, biomimetic structure, gradient structure, or random microstructure, with the size of a single microstructure being 1-50 μm.

4. The flexible three-dimensional force tactile sensor according to claim 1, characterized in that, An interdigitated electrode consists of a common negative electrode and four individual positive electrodes.

5. A method for fabricating a flexible three-dimensional force-tactile sensor according to any one of claims 1 to 4, characterized in that, include: (1) Preparation of protrusions; The polydimethylsiloxane prepolymer and curing agent are mixed evenly at a mass ratio of 10:1, poured into a mold, de-bubbled, and then covered with a PMMA sheet. The mixture is then heated and cured to obtain a raised surface. (2) Preparation of the sensitive layer; First, the polydimethylsiloxane prepolymer and curing agent are mixed evenly in a mass ratio of 10:1, poured into a mold with microstructure, defoamed, and then heated to cure, resulting in a high-modulus flexible material with microstructure on one side. Conductive ink is then sprayed onto the microstructure side of the high-modulus flexible material to obtain a low-sensitivity layer. Then, Ecoflex A liquid and Ecoflex B liquid are mixed evenly in a volume ratio of 1:1, poured into a mold with microstructure, defoamed, and cured at room temperature to obtain a low-modulus flexible material with microstructure on one side. Conductive ink is then sprayed onto the microstructure side of the low-modulus flexible material to obtain a highly sensitive layer. Finally, the low-sensitivity layer is cut into a square ring, and the high-sensitivity layer is cut into a square, ensuring that the square size of the high-sensitivity layer is consistent with the internal blank size of the square ring of the low-sensitivity layer, and that the two are concentric with corresponding parallel sides; ensuring that the microstructures of the two are on the same side, the high-sensitivity layer is assembled into a single unit by splicing it into the internal blank space of the square ring of the low-sensitivity layer, and then attaching it to the opposite side of the microstructure using PI tape, resulting in a sensitive layer with a microstructure on the lower surface and a PI tape-bonded upper surface; (3) Fabrication of the interdigitated electrode layer; Interdigitated electrode layers are obtained by laser etching of rectangular PET electrodes with metallic silver on their surface; (4) Fabrication of a flexible three-dimensional force-tactile sensor; The lower surface of the protrusion prepared in (1) is bonded to the upper surface of the sensitive layer prepared in (2) with glue. Then, the lower surface of the sensitive layer is assembled face to face with the interdigital electrode layer and encapsulated with PI tape to obtain a flexible three-dimensional force tactile sensor.

6. The preparation method according to claim 5, characterized in that, (2) The conductive ink is composed of CNTs, TPU and DMF, wherein the concentration of CNTs is 2 mg / ml and the concentration of TPU is 0.67 mg / ml.

7. The preparation method according to claim 5, characterized in that, (2) Before spraying conductive ink onto medium-high modulus flexible materials and low modulus flexible materials, plasma surface treatment is performed, and then the materials are placed at 80°C for spraying treatment.

8. A flexible three-dimensional force tactile sensor, characterized in that, The sensitive layer described in claim 1 is a material with a laterally varying modulus, constructed using a pore-forming method, an ultraviolet curing method, or a 3D multi-material printing method, or a material with a laterally varying sensitivity, constructed by creating a microstructure with a laterally varying size on the lower surface of the sensitive layer.

9. An application of the flexible three-dimensional force tactile sensor as described in claim 1 or 8, characterized in that, Used for measuring three-dimensional forces on an interface, performing slip detection, or game control.

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